1. Field of the Invention
This invention relates to a finder indication optical system in a single-lens reflex camera.
2. Related Background Art
A prior-art finder optical system in a single lens reflex camera is shown in FIG. 1 of the accompanying drawings. As shown in FIG. 1, in the prior-art finder optical system, an object image on a focusing screen 1 is observed through a pentagonal prism 2 and an eyepiece 3, and information such as aperture value and shutter speed is observed through the eyepiece 3 by light emerging from an indicator 4 being reflected by reflecting mirrors 5 and 6 and being passed through a light transmitting portion 2b provided on the upper portion of a third reflecting surface 2a of the pentagonal prism 2.
Photometry for obtaining proper exposure is accomplished by light emerging substantially from the center of the focusing screen 1 and light reflected by the roof surface 2c and third surface 2a of the pentagonal prism 2 being condensed by a condensing lens 7 and being received by a light receiving element 8.
In recent years, however, with the advance of the photometering method, not only the central portion but also the marginal portion of the image field has come to be photometered precisely and therefore, the expanse of a light beam necessary for photometry has become large and the reflection area of said third reflecting surface 2a has come to be enlarged in the vertical direction.
Therefore, the light transmitting portion 2b located on the upper portion of the third reflecting surface 2a is forced up (12b) as shown in FIG. 2 of the accompanying drawings, and as a result, as shown in FIG. 3 of the accompanying drawings, the indication 20 of photographing information rises too much upwardly in the field of view and the distance thereof from the object image 21 becomes long, and this has led to a problem that it becomes difficult to observe the object image 21 and the indication 20 of the photographing information at a time.
In order to solve this problem, it would occur to mind to place a deflection prism in the optical path of the indication optical system, but if a deflection prism is provided in the optical path of the indication optical system, astigmatism will be created in an indicating light beam, and this gives rise to a problem that the indication is not seen clearly.